Third lecture

Ecosystem

An ecosystem is a self-sustaining, dynamic community of plants and animals in relation to their physical environment.

SystemInteracting parts that share common location in space, time and/or function

Ecosystem

• All of the organisms living in a particular place as well as the chemical/physical factors with which they interact.

• Range in size from small (like aquarium) to large (like forest)

• E.g. desert ecosystem: organisms that live there (cacti, snakes, rodents), soil chemistry, average rainfall, temperatures etc.

Any ecosystem is composed of:

1-Abiotic components (nonliving factors) such as: light, temperature, water, oxygen, minerals, pH and soil.

2-Biotic components (living things) such as:

i-Producers (autotrohps): they are the green plants since they produce organic compounds that serve as food.

AutotrophsA groups of organisms that can use the energy in sunlight to convert water and carbon dioxide into Glucose (food) Ex. Plants and Algae

Autotrophs

• Chemotrophs– Autotrophs that get their energy from inorganic

substances, such as salt

– Live deep down in the ocean where there is no sunlight

– Ex. Bacteria and Deep Sea Worms

ii-Consumers (heterotrophs): Organisms that do not make their own food:

• Primary consumers (herbivores): Organisms that feed directly on green plants.

• Secondary consumers: Are carnivores that prey on the primary consumers.

• Tertiary consumers: Predators on the secondary consumers and primary consumers.

• detritivores -consumers that get their energy from detritus-nonliving organic material.

iii-Decomposers:

• These organisms decompose organic material in ecosystem and transfer chemical elements in inorganic forms to reservoirs such as soil, water, and air.

• These chemical elements are cycled, or returned to the environment, where other living things use them again.

Consumers (heterotrophs)

They consume other organisms in order to live

Ex. Rabbits, Deer, Mushrooms

Heterotrophs 1.Scavengers/Detritivores: feed on the tissue

of dead organisms (both plans and animals).

Ex. Vultures, Crows, and Shrimp

Heterotrophs

2.Herbivores: eat only plants

Ex. Cows, Elephants, Giraffes

Heterotrophs

3.Carnivores: eat only meat

Ex. Lions, Tigers, Sharks

Heterotrophs

4.Omnivores: eat both plants and animals. Ex. Bears and Humans

Heterotrophs

5.Decomposers: absorb any dead material and break it down into simple nutrients or fertilizers. Ex. Bacteria and Mushrooms